IN-VIVO BRAIN SIZE, HEAD PERIMETER, AND INTELLIGENCE IN A SAMPLE OF HEALTHY ADULT FEMALES

The issue of the connection between brain size and intelligence has long been of interest to psychology. A review of past research using external head size measures as estimates of internal brain size indicates that head size-IQ correlations are typically in the order of r = 0.10 to 0.30 (mean r = 0.194). Today, a more direct and accurate measure of brain size is afforded by the advent of magnetic resonance imaging (MRI). In the present study the relationship between brain size (measured via MRI), head size, and intelligence was examined in a sample of 40 healthy, right-handed females (ages 20 to 30 years). Whereas head size correlated r = 0.109 (NS) with full scale IQ, brain size and IQ correlated r = 0.395 (P < 0.05). It is clearly indicated that there is a positive relationship between the size of the brain and intelligence.